Conventional equipment of this nature comprises a portal frame or a tunnel roof carrying one or more elevatable horizontal rotary brushes for scrubbing the front, top and rear surfaces of the vehicle as well as at least one pair of symmetrically disposed laterally oscillatable rotary vertical brushes for scrubbing front, side and surfaces of respective halves of the vehicle. Such brushes and their mountings have been disclosed, for example, in my U.S. Pat. Nos. 3,618,152, 3,633,231 and 3,725,967.
In such a system the vertical brushes are generally positioned close to each other, near the centerline of an oncoming vehicle, at the beginning of a washing cycle and move apart along the front of the vehicle as the latter advances relatively to the guide structure. Since the forward end of a vehicle is usually dirtier than the rest of its body, this relatively short contact with the vertical brushes may not suffice for a thorough cleaning of the vehicular front surface, especially near its center.